The motivation which gave the main impetus to the present invention is primarily economic in nature, namely minimize the scrapping of remnants resulting from the saw-cutting of truck floor boards to shorter length so as to fit trucks of shorter length. These remnants ought to be fully utilized in the forming of truck flooring, and as will be seen indeed they are as per the present invention.
Flooring which is to be suitable for utilization in trucks requires that the floor boards be of substantially greater strength than is customary for other flooring applications. The reason for this is quite evident, namely the cargo carried by trucks is a substantial load on the flooring. Truck floor boards are constructed usually in tiers of laminations. The floor board manufacturers usually situate their factories at, or near the timber lands where the trees or vegetation--suitable for truck flooring--is grown. The boards are provided in standard widths and thicknesses at the will of the floor board manufacturer; as to the lengths of the boards, these are also largely standardized by the floor board manufacturer, although the purchaser will usually be accommodated to meet his own separate needs. Because the standard lengths are quite great--twenty feet and greater, even about fifty feet are common--the manufacturer of the laminated floor boards finds it necessary to do some jointing of his own; hook jointing is commonly employed, and most of the longer boards will exhibit at least one hook joint. Such hook jointing is made during the course of the formation of the laminations which constitute the standard floor board, and should be differentiated from the jointing of completed such boards.
Floor boards which are to be assembled in the United States, or more generally in North America, are available from two principal geographic sources: North America (United States, Canada), and Malaysia. There may be other geographic sources, but economic considerations rule them out. The boards stemming from North American sources are available in soft woods, such as pine, and in the somewhat harder oak. Malaysian boards stem from hardwoods indigenous to that country; generally speaking, the Malaysian boards can be manufactured with strength characteristics comparable to those of North American boards, and in some applications, even stronger. However, there is an even more compelling reason for preference for the Malaysian boards, namely costs.
The cost of Malaysian floor boards is about 50% of the cost of comparable floor boards which stem from North American sources, with the cost of transportation and importation taken into account. However such a cost comparison must be qualified or circumscribed by a relevant limiting restriction: as of the early and middle 1980s, the importation of Malaysian floor boards into North America is, practically speaking, economical for just a few standard lengths, all under 40 feet. Although Malaysian as well as North American board manufacturers are willing to provide their purchasers with boards constructed or cut to almost any desired length, problems which are inherent in the trans-Pacific shipment, further restrict the choice of standard board lengths. Among these problems are: limitations dictated by size or shape of shipping vessels and shipping containers; the greater likelihood of the longer length boards to incur damage during shipment, especially during the loading and unloading stages; the long leadtime (as long as six months), from the date of purchase by the North American purchaser to date of receipt of the imported Malaysian boards and their availability for inventory and production needs. Routinely, production material needs were far ahead of inventory. As a result longer boards were shortened to meet the production needs. This action resulted in considerable wastage by generations of unused board remnants. Standard lengths of 20 feet and 40 feet are among the remaining practical choices for imported Malaysian boards. The description hereinafter will be given by way of example, in terms of 20 foot standard length boards, although similar considerations apply to 40 foot long boards, or boards of still another initial standard length.
Wastage of this kind, or wastage engendered by inventory shortage as discussed above, were major economic factors which directed finding a means for end-jointed boards. It was thought that the jointing of floor boards was not practical because the joints were too weak to withstand the heavy loading, and vertically directed loading at that, of the cargoes carried by the trucks.
Further investigations by workers in this field indicated that if jointing of floor boards for truck use were to be successful after all, finger jointing offered good promise. Even at that, another obstacle stood in the way, namely orientation of the finger joint profile. Where two floor boards are to be finger-jointed together end to end, each such end before it is intermeshed with its engaging end of the other board, will exhibit a profile or contour whose shape resembles that of a rack gear defined by gear teeth, peaks and valleys. These "racks" are fully visible upon generation of the finger joint profile, but before the preliminary jointing together to be followed by gluing and finishing. The so visible profiles admit of several orientations: (1) the peaks of the rack gear teeth --and for that matter, their valleys--extend parallel to the thickness direction, that is parallel to the shortest dimension (usually) of the board. This means that upon completion of the preliminary jointing and indeed of final jointing, there will remain visible on the top surface of the jointed boards and hence on the finished floor surface, a zig-zag pattern. The truck floor constructing manufacturer favors this, because it is a relatively strong joint capable of withstanding the vertical loading by the truck's cargo. However, the purchaser of the floor or of the truck with the floor installed in it, objects to the zig-zag pattern for aesthetic reasons. The peaks and valleys of the rack gear teeth extend parallel to the width direction of the board, that is parallel to the second greatest dimension of the board; usually, the length direction is the greatest. With this orientation, once the two boards have been jointed, even merely preliminarily, visible on their top surface, though perhaps even barely visible at that, would be a straight line which corresponds to the width of the boards. This line, would be visible, perhaps just barely visible, also on the finished truck floor. This orientation has been utilized in finger joint applications other than for truck flooring; see for example brochures published by manufacturers of finger joint woodworking machinery, for example brochure published by Lewyn Machinery Company, Smyrna, Georgia, U.S.A., their Catalog CE-345L-1, directed to IMC woodworking machinery, published October, 1984; see also brochure published by Smi Stebar Machinery, Inc., Cambridge, Ontario, Canada, their brochure directed to "Economical Finger Jointing System".
Although acceptable for other woodworking applications, the "straight-line-visible" finger joint profile had not been favorably considered by truck floor board manufacturers because they considered such joints to be too weak to withstand the vertical cargo loading in trucks, and yet this is the orientation which their purchasers desired.
Applicants have recently made refinements in the technique of finger jointing, and in "straight-line-visible" finger jointing, and surprisingly have produced joints which are from about 70% to 80% as strong as laminated floor boards without finger joints, and therefore suitable for truck flooring. This development has made the present invention practical.
It is the general object of the invention to provide a truck floor employing finger jointing of floor boards such that the scrapping of remnant floor boards is minimized and instead these remnant boards are utilized in making lengths of floor boards destined for use in the laying of truck floors.
It is also an object of the invention to provide truck floor methodology utilizing finger jointing techniques whereby floor boards of given standard lengths can be converted to floor boards of some other standard lengths, lesser or greater lengths than the standard lengths of the original floor boards.
Notice, in the just stated object of the invention, the creation of floor boards of greater than original lengths, as well as the creation of floor boards of lesser than original length. Historically speaking, the creation of the floor boards of lesser lengths has posed the difficulties mentioned in the introduction of the specification; once this problem was overcome, similar concepts could be applied to the creation of floor boards of greater than original length.